1. Field of the Invention
The invention relates generally to the field of photography, and in particular to a film cassette containing roll film.
2. Description of the Prior Art
Commonly assigned U.S. Pat. No. 5,031,852, issued Jul. 16, 1991 discloses a film cassette wherein a film spool comprises a spool core supported for rotation in an unwinding direction to thrust a leader section of a film roll coiled about the spool core to the exterior of the cassette and in a winding direction to return the film leader to the interior of the cassette, and a pair of flanges positioned along the spool core to overlie opposite sides of the film roll to radially confine the film roll within skirted peripheries of the flanges. The flanges have respective central openings through which the spool core coaxially extends to normally permit the flanges and the spool core to be independently rotated in the two directions. According to the invention, hooks are rotatably fixed to the spool core for initial rotation with the spool core relative to the flanges in the unwinding direction, for movement into engagement holes in at least one of the flanges to make the flange rotate in unity with the spool core when the spool core is rotated further in the unwinding direction, to improve the ability of the film spool to thrust the film leader from the cassette, and in the film winding direction, for movement out of the engagement holes in the flange to permit the flange to be independently rotated when the spool core is rotated further in the winding direction, to substantially ensure the film leader can be rewound within the skirted periphery of the flange.
It has been found that by fixing at least one of the flanges to the spool core during unwinding rotation of the spool core, as contrasted with allowing each of the flanges to remain rotatable independently of the spool core as in commonly assigned U.S. Pat. No. 4,834,306 and U.S. Pat. No. 4,848,693, there is immediately effected a frictional relationship between the outermost convolution of the film roll and the skirted periphery of the fixed flange which improves the ability of the film spool to thrust the film leader to the exterior of the cassette. In particular, the frictional relationship increases the pushing force the film spool applies to the film leader to propel the leader out of the cassette. Moreover, it has been found that by allowing both of the flanges to be rotated independently of the spool core during winding rotation of the spool core, as in commonly assigned U.S. Pat. Nos. 4,834,306 and 4,848,693, it is substantially ensured that the film leader will be rewound within the skirted peripheries of the flanges without being obstructed by the skirted peripheries.